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(11) | EP 0 964 538 A3 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Optical transmitter and optical transmission system using polarisation modulation |
| (57) An optical transmitter for use in an optical transmission system comprises a light
source (1), an intensity modulator (2) for modulating the intensity of light output
from the light source according to NRZ data (101) that is transmission data, and a
polarization modulator (4) for modulating the polarization of the output from the
intensity modulator according to an alternating signal (102). Each bit of the alternating
signal has substantially the same time interval as each bit of the transmission data.
Instead of the NRZ data, an RZ signal may be used for modulation, and instead of the
alternating signal, a signal may be used that inverts the logic for those bits having
a value for the larger intensity of the modulated light. A phase modulator using a
bit rate frequency sine wave as a modulation input may be inserted between the intensity
modulator and the polarization modulator. In this case, the intensity and phase modulators
may be connected in the reverse order. In addition, at least one optical amplifier
may be inserted between any adjacent modulators. |